i was there... she was nowhere near sold out
It was part of the F1 line-up, so anybody who bought a ticket to see the race, could go and see her. Her set fell just before the race started so that gave her a lot of benefits in terms of crowd. But in reality, other than the few hundred "hipster" teen girls standing very close at the front, people were sitting down and lying down eating fries behind. I thought it was very rude and appalling. Nobody sang along either and she clearly felt awkward and didn't know what to do with that lame ass crowd.
Most came mid-set btw. I was there 15 minutes before her set started and there were only about 4 - 5 rows of people in front of me.